KR20150135325A - Water-absorbent resin composition production method - Google Patents

Abstract

The present invention relates to a process for producing a water absorbent resin composition comprising water absorbent resin particles and additive particles, wherein the water absorbent resin composition comprises a water absorbent resin composition Method. The method for producing the water absorbent resin composition includes a resin particle preparation step (s1) and a mixing step (s2). In the mixing step (s2), the water absorbent resin particles and the additive particles prepared in the resin particle preparing step (s1) are mixed in multiple stages using a plurality of mixing devices to obtain a water absorbent resin composition.

Description

TECHNICAL FIELD [0001] The present invention relates to a water absorbent resin composition,

The present invention relates to a process for producing an water absorbent resin composition, and more particularly to a process for producing an water absorbent resin composition comprising a mixing process of mixing water absorbent resin particles and additive particles.

The absorbent resin is widely used as a sanitary material such as paper diapers and sanitary articles, daily necessities such as pet sheets, industrial materials such as absorbent sheets for food, exponential materials for cables and anti-condensation materials, And the like. The water absorbent resin is used as a sanitary material in particular among the above applications.

Such a water absorbent resin is usually a polymer crosslinked with hardness. Examples of the water absorbent resin include starch-based water absorbent resins such as a hydrolyzate of a starch-acrylonitrile graft copolymer (see Patent Document 1), a neutralized product of a starch-acrylic acid graft copolymer (see Patent Document 2) (See Patent Document 3), and polyacrylic acid partial neutralized products (see Patent Document 4, Patent Document 5, Patent Document 6), and the like are known.

Examples of characteristics that the water absorbent resin should have include excellent absorption characteristics and handling characteristics. The excellent absorption property means that the absorption capacity, the absorption speed and the liquid permeability when the aqueous liquid such as body fluids are brought into contact with the water absorbent resin are good. In addition, the handling property is excellent when the absorbent resin is absorbed by the absorbent resin when the absorbent resin and the fibrous substrate are used, and exhibits excellent fluidity and is less adhered to the apparatus for producing the absorbent. In addition, due to an increase in the demand for adult diapers due to aging, additional functional properties such as antibacterial and deodorization for absorbent resins are also required.

A technique of adding additive particles to water absorbent resin particles has been proposed for the purpose of improving such absorption properties, handling properties, and addition function characteristics. For example, there have been proposed techniques (Japanese Patent Application Laid-Open Nos. 7 to 9) for improving the gel-blocking property and liquid-permeability at the time of urination of a diaper, techniques for improving moisture absorption blocking resistance (see Patent Document 10 to Patent Document 15) A technique for imparting deodorization (see Patent Document 16 to Patent Document 19) has been proposed. Further, there has been proposed a technique of adding powder of a water-soluble metal soap to the water-absorbent resin particles (see Patent Document 20), and a technique of adding powder of a polyvalent metal salt to the water-absorbent resin particles (see Patent Document 21 and Patent Document 22) .

Japanese Patent Publication No. 49-43395 Japanese Patent Application Laid-Open No. 51-125468 Japanese Patent Laid-Open No. 52-14689 Japanese Patent Application Laid-Open No. 62-172006 Japanese Patent Application Laid-Open No. 57-158209 Japanese Patent Application Laid-Open No. 57-21405 Specification of European Patent No. 629411 Japanese Unexamined Patent Application Publication No. 2003-176421 Japanese Patent Laid-Open No. 11-286611 Japanese Patent Application Laid-Open No. 2000-93792 U.S. Patent No. 6,124,391 U.S. Patent No. 5985944 Japanese Patent Application Laid-Open No. 9-241322 Japanese Patent Application Laid-Open No. 64-4653 U.S. Patent Application Publication No. 2005/113252 International Publication No. 2005/10102 brochure Japanese Patent Application Laid-Open No. 9-248454 Specification of European Patent No. 1257596 Japanese Unexamined Patent Application Publication No. 10-120921 U.S. Patent Application Publication No. 2005/118423 U.S. Patent Application Publication No. 2006/73969 U.S. Patent No. 6300275

As a mixing method of mixing the water absorbent resin particles and the additive particles in the production of the water absorbent resin composition comprising the water absorbent resin particles and the additive particles, a dry blend method (a method of mixing the powders) is generally adopted, A number of continuous or batch-type powder mixing apparatuses for realizing a blending method have been proposed. Examples of the powder mixing apparatus include a paddle blender, a ribbon blender, a rotary blender, a low tumbler, a plunger mixer, a cylindrical mixer, a V-shaped mixer, a ribbon- A humidifier mixer, an air flow mixer, and the like are known.

However, the technique of adding the additive particles to the water absorbent resin particles to impart various functions has been known, but its function is not sufficient. For the purpose of uniformly mixing the additive particles, the mixing using the powder mixing device is performed for a long time, It is necessary to use the additive particles of the above-mentioned additive particles.

In recent years, the water absorbent resin production facility has been enlarged and continuously produced in order to increase the demand and reduce the cost. It is necessary to mix the additive particles in a large amount of the water absorbent resin particles in a short period of time. However, by merely enlarging the facilities by using the conventional powder mixing apparatus, even if mixed for a long time, the water absorbent resin composition And the additive function of the additive particles can not be sufficiently exerted.

An object of the present invention is to provide a water absorbent resin composition which is sufficiently exhibited by the additive function of the additive particles such as moisture absorption blocking properties while maintaining excellent absorption properties in the method of producing the water absorbent resin composition comprising the water absorbent resin particles and the additive particles And to provide a method of manufacturing the same.

The present invention relates to a method for producing an water absorbent resin composition comprising water absorbent resin particles and additive particles,

A process for producing a water-absorbent resin, comprising the steps of:

And a mixing step of mixing the water absorbent resin particles prepared in the resin particle preparing step with the additive particles in a multistage manner using a plurality of mixing devices to obtain an water absorbent resin composition.

Further, in the method for producing the water absorbent resin composition of the present invention,

A primary mixing step of primary mixing the water absorbent resin particles and the additive particles using a first mixing device,

It is preferable that the primary mixture obtained in the primary mixing step has a secondary mixing step of secondary mixing using the second mixing apparatus until the additive particles are uniformly dispersed.

Further, in the method for producing the water absorbent resin composition of the present invention, it is preferable that the primary mixing step further includes a plurality of mixing steps.

Further, in the method for producing the water absorbent resin composition of the present invention,

The first mixture obtained in the first mixing step is vapor-phase transported from the first mixing device to the second mixing device through the first transfer pipe disposed between the first mixing device and the second mixing device, A first transport mixing step of mixing the primary mixture in the transport piping,

The secondary mixture obtained in the secondary mixing step is discharged from the second mixing apparatus through a second transportation pipeline for discharging from the second mixing apparatus and vapor-phase transported to mix the secondary mixture in the second transportation pipeline And a second transport mixing step for carrying out the second transport mixing step.

In the method for producing the water absorbent resin composition of the present invention, it is preferable that the first mixing device and the second mixing device are devices of different mixing types.

Further, in the method for producing the water absorbent resin composition of the present invention, the additive particles are preferably particles made of an inorganic material.

In the method of producing the water absorbent resin composition of the present invention, it is preferable that the throughput of the water absorbent resin particles in one primary mixing treatment in the primary mixing step is more than 0 and not more than 40,000 kg.

(Effects of the Invention)

According to the present invention, a method for producing a water absorbent resin composition comprising water absorbent resin particles and additive particles includes a resin particle preparation step and a mixing step. In the mixing step, the water absorbent resin particles and the additive particles prepared in the resin particle preparing step are mixed in multiple stages using a plurality of mixing devices to obtain a water absorbent resin composition.

In the method of producing the water absorbent resin composition of the present invention, since the water absorbent resin particles and the additive particles are mixed in multiple stages using a plurality of mixing apparatuses, the water absorbent resin composition in which the additive particles are uniformly dispersed in a short time without damaging the surface of the water absorbent resin particles Can be obtained. Accordingly, it is possible to obtain a water absorbent resin composition in which the additive particles such as moisture absorption blocking resistance and the like exhibit sufficient additional functions while maintaining excellent absorption properties.

Further, when the water absorbent resin particles and the additive particles are mixed with each other in a production facility having a large production amount of the water absorbent resin composition, it becomes difficult to obtain the water absorbent resin composition in which the additive particles are uniformly dispersed. In the method of producing the water absorbent resin composition of the present invention, the water absorbent resin particles and the additive particles are mixed in a multistage manner using a plurality of mixing devices, so that even when the water absorbent resin particles and the additive particles are mixed in an enlarged production facility, The dispersed water absorbent resin composition can be obtained in a short time.

Further, according to the present invention, the mixing process has a primary mixing step and a secondary mixing step. In the first mixing step, the water absorbent resin particles and the additive particles are first mixed using a first mixing apparatus. In the secondary mixing step, the primary mixture obtained in the primary mixing step is secondarily mixed in the primary mixture using the second mixing apparatus until the additive particles are uniformly dispersed. Thus, the water absorbent resin composition in which the additive particles are uniformly dispersed in a short time without damaging the surface of the water absorbent resin particles can be obtained.

Further, according to the present invention, the primary mixing step further includes a plurality of mixing steps. Since the primary mixing step of primary mixing the water absorbent resin particles and the additive particles further comprises a plurality of mixing steps, the total amount of the water absorbent resin particles and the additive particles, which are the raw materials necessary for preparing the water absorbent resin composition, In a plurality of stages at each stage of mixing in order to obtain a primary mixture. In this way, the primary mixture obtained by dividing the primary mixture in each mixing step in the primary mixing step is secondarily mixed in the secondary mixing step, whereby the water absorbent resin composition in which the additive particles are more uniformly dispersed can be obtained in a short time.

Further, according to the present invention, the mixing process further has a first transport mixing step and a second transport mixing step. The first transport mixing step is a step of vapor-phase transporting the first mixture obtained in the first mixing step through a first transporting pipe disposed between the first mixing device and the second mixing device, Mix. Further, the second transport mixing step mixes the secondary mixture in the second transport pipe by vapor-phase transporting the second mixture obtained in the second mixing step through a second transport pipe for discharging the second mixture from the second mixing device. As described above, the primary mixture obtained in the primary mixing step using the first mixing device is also mixed at the time of vapor phase transportation in the first transportation pipe, and the secondary mixture obtained in the secondary mixing step using the second mixing device The water-absorbing resin composition in which the additive particles are more uniformly dispersed can be obtained in a short time.

Further, according to the present invention, the first mixing device and the second mixing device are different mixing devices. As described above, in the first mixing apparatus used in the first mixing step in which the water absorbent resin particles and the additive particles are first mixed to obtain a first mixture, and a second mixing step in which the first mixture is secondarily mixed to obtain a second mixture And the second mixing apparatuses used are different mixing systems, so that the water absorbent resin composition in which the additive particles are more uniformly dispersed can be obtained in a short time.

Further, according to the present invention, the additive particles to be mixed with the water absorbent resin particles are particles made of an inorganic material. Even when such an inorganic particle is used as an additive particle, a water absorbent resin composition in which the inorganic particle is uniformly dispersed can be obtained in a short time.

According to the present invention, in the primary mixing step in which the water absorbent resin particles and the additive particles are first mixed to obtain a primary mixture, the throughput of the water absorbent resin particles in one primary mixing treatment is more than 0 and not more than 40,000 kg . As a result, the dispersibility of the additive particles in the primary mixture obtained in the primary mixing step can be improved.

The objects, features, and advantages of the present invention will become more apparent from the following detailed description and the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a process diagram showing a method for producing an water absorbent resin composition according to an embodiment of the present invention. Fig.
Fig. 2 is a process diagram showing an example of details of the resin particle preparation step (s1).
3 is a process diagram showing an example of details of the mixing process (s2).
4 is a diagram showing an example of the configuration of the mixing equipment 1 for carrying out the mixing step s2.
5 is a diagram showing the configuration of the measuring apparatus 3 used for evaluating the absorption ability under pressure.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

Hereinafter, the present invention will be described in detail. However, the scope of the present invention is not limited to these descriptions, and other than the following examples can be appropriately changed without departing from the spirit of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a process diagram showing a method for producing an water absorbent resin composition according to an embodiment of the present invention. Fig. The method for producing the water absorbent resin composition of the present embodiment is a method for producing an water absorbent resin composition comprising a particulate water absorbent resin (hereinafter referred to as "water absorbent resin particle") and a particulate additive (hereinafter referred to as " (S1), a mixing step (s2), and a collecting step (s3).

[Resin Particle Preparation Step]

Fig. 2 is a process diagram showing an example of details of the resin particle preparation step (s1). The resin particle preparing step (s1) is a step of preparing the water absorbent resin particles. For example, as shown in Fig. 2, the polymerization step (s11), the thickening step (s12), the surface cross-linking step (s13) And a grinding step (s15) and a classification step (s16).

<Polymerization Step>

The polymerization step (s11) is a step of polymerizing a water-soluble ethylenically unsaturated monomer to obtain an water absorbent resin. The method of polymerizing the water-soluble ethylenic unsaturated monomer is not particularly limited, and typical aqueous polymerization methods such as an aqueous solution polymerization method, an emulsion polymerization method and a reversed-phase suspension polymerization method are used.

In the aqueous solution polymerization method, polymerization is carried out, for example, by heating an aqueous solution of a water-soluble ethylenic unsaturated monomer, an internal cross-linking agent and a water-soluble radical polymerization initiator, if necessary, with stirring. In this aqueous solution polymerization method, water is treated as a liquid medium, and the water-soluble ethylenic unsaturated monomer is brought into an aqueous solution state to carry out a polymerization reaction.

In the reversed-phase suspension polymerization, polymerization is carried out, for example, by heating an aqueous solution of a water-soluble ethylenic unsaturated monomer, a surfactant, a hydrophobic polymer dispersant, a water-soluble radical polymerization initiator and an internal crosslinking agent in a petroleum hydrocarbon dispersion medium under stirring. In this reversed-phase suspension polymerization method, water and a petroleum hydrocarbon dispersion medium are treated as a liquid medium, and an aqueous solution of a water-soluble ethylenic unsaturated monomer is added to a petroleum hydrocarbon dispersion medium to perform a polymerization reaction.

In the present embodiment, a reversed phase suspension polymerization method is preferable from the viewpoint of precise polymerization reaction control and control of a wide particle diameter. Hereinafter, as an example of an embodiment of the present invention, a method of producing an water absorbent resin by a reversed-phase suspension polymerization method will be described.

Examples of the water-soluble ethylenic unsaturated monomer used in the raw material of the water absorbent resin include (meth) acrylic acid ("(meth) acrylic" means "acrylic" and "methacryl". Monomers having an acid group such as 2- (meth) acrylamide-2-methylpropanesulfonic acid and maleic acid, and salts thereof; Nonionic unsaturated monomers such as (meth) acrylamide, N, N-dimethyl (meth) acrylamide, 2-hydroxyethyl (meth) acrylate and N-methylol (meth) acrylamide; Amino group-containing unsaturated monomers such as diethylaminoethyl (meth) acrylate and diethylaminopropyl (meth) acrylate, and quaternary amides thereof. These may be used alone or in combination of two or more.

Examples of the alkaline compound used in the case of neutralizing the monomer having an acid group to form a salt include compounds such as lithium, sodium, potassium, and ammonium. More specifically, examples thereof include sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, and ammonium carbonate.

Among the water-soluble ethylenically unsaturated monomers, (meth) acrylic acid and salts thereof are exemplified from the viewpoint of industrial availability.

When the monomer having an acid group is neutralized, the degree of neutralization thereof is preferably 30 to 90 mol% of the acid group of the water-soluble ethylenic unsaturated monomer. When the degree of neutralization is 30 mol% or more, the acid group is easily ionized and the absorption ability is prevented from being lowered. When the neutralization degree is 90 mol% or less, it is possible to suppress the occurrence of problems such as safety when used as a sanitary material.

In the present embodiment, the water-soluble ethylenic unsaturated monomer is used as an aqueous solution. The monomer concentration of the water-soluble ethylenically unsaturated monomer aqueous solution is preferably 20% by mass to the saturated concentration.

The aqueous solution of the water-soluble ethylenic unsaturated monomer may contain a chain transfer agent, a thickening agent and the like as necessary. Examples of the chain transfer agent include compounds such as thiols, thiol acids, secondary alcohols, hypophosphoric acid, and phosphorous acid. These may be used alone or in combination of two or more. Examples of the thickening agent include carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, polyethylene glycol, polyacrylic acid, polyacrylic acid neutralized product, polyacrylamide and the like.

Examples of the petroleum hydrocarbon dispersion medium include aliphatic hydrocarbons having 6 to 8 carbon atoms such as n-hexane, n-heptane, 2-methylhexane, 3-methylhexane, Alicyclic hydrocarbons such as hydrocarbons, cyclohexane, methylcyclohexane, cyclopentane, methylcyclopentane, trans-1,2-dimethylcyclopentane, cis-1,3-dimethylcyclopentane and trans-1,3- , Aromatic hydrocarbons such as benzene, toluene, xylene and the like. Among them, aliphatic hydrocarbons having 6 to 8 carbon atoms such as n-hexane, n-heptane, 2-methylhexane, 3-methylhexane, and n-octane from the viewpoint of industrial availability and safety; Alicyclic hydrocarbons having 6 to 8 carbon atoms such as cyclohexane, methylcyclopentane and methylcyclohexane are more suitably used. These petroleum hydrocarbon dispersing agents may be used alone or in combination of two or more.

Among these petroleum hydrocarbon dispersants, n-heptane and cyclohexane are preferably used from the viewpoints of favorable reversed-phase suspension state, easy particle diameter acquisition, industrial availability, and stable quality . In addition, suitable results can be obtained by using commercially available exoheptane (n-heptane manufactured by Exxon Mobil Corporation, containing 75 to 85% of hydrocarbons of the isomer) as an example of the hydrocarbon compound.

The amount of the petroleum hydrocarbon dispersion medium to be used is generally 50 to 600 parts by mass, preferably 50 to 600 parts by mass, per 100 parts by mass of the water-soluble ethylenically unsaturated monomer aqueous solution, from the viewpoint of uniformly dispersing the aqueous ethylenically unsaturated monomer aqueous solution and controlling the polymerization temperature. To 400 parts by mass is more preferable, and 50 parts by mass to 200 parts by mass is more preferable.

In the reversed-phase suspension polymerization, a surfactant and, if necessary, a hydrophobic polymer dispersant are used in order to disperse a water-soluble ethylenically unsaturated monomer aqueous solution into a petroleum hydrocarbon dispersion medium to obtain more stable polymer particles. From the viewpoint that the polymerization is completed stably without any abnormality, the surfactant and the hydrophobic polymer dispersant are present before the polymerization of the water-soluble ethylenically unsaturated monomer aqueous solution to sufficiently disperse the water-soluble ethylenic unsaturated monomer aqueous solution in the petroleum hydrocarbon hydrogen dispersant, When the polymerization can be carried out after stabilizing the enemy, the timing of addition is not particularly limited. Although there are some exceptions in view of the existing technology, surfactants and hydrophobic polymer dispersants are generally dissolved or dispersed in a petroleum hydrocarbon dispersion medium before adding the water-soluble ethylenically unsaturated monomer aqueous solution.

Examples of the surfactant used for maintaining the dispersion stability during polymerization include sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyglycerin fatty acid esters, polyoxyethylene glycerin fatty acid esters, sucrose fatty acid esters, sorbitol fatty acid esters , Polyoxyethylene sorbitol fatty acid ester, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene castor oil, polyoxyethylene hardened castor oil, alkylallyl formaldehyde condensed polyoxyethylene ether, polyoxyethylene polyoxypropyl Nonionic surfactants such as alkyl ethers, polyethylene glycol fatty acid esters, alkyl glucosides, N-alkyl glucoamides, polyoxyethylene fatty acid amides, and polyoxyethylene alkylamines; fatty acid salts, alkylbenzenesulfonic acid salts, Polyoxyethylene alkylphenyl ether sulfuric acid ester salts, polyoxyethylene alkyl ether sulfonic acid and salts thereof, polyoxyethylene alkylphenyl ether phosphoric acid and salts thereof, polyoxyethylene alkyl ether phosphoric acid and And an anionic surfactant such as a salt thereof. These may be used alone or in combination of two or more.

Of these surfactants, at least one member selected from the group consisting of polyglycerin fatty acid esters, sucrose fatty acid esters and sorbitan fatty acid esters is preferable from the viewpoint of dispersion stability of the monomer aqueous solution.

The amount of the surfactant to be added is preferably 0.01 to 5 parts by mass, more preferably 0.05 to 3 parts by mass, per 100 parts by mass of the water-soluble ethylenic unsaturated monomer aqueous solution. The addition amount of the surfactant is 0.01 part by mass or more so that the dispersion stability of the water-soluble ethylenically unsaturated monomer aqueous solution can be prevented from being lowered, and it is economically advantageous since it is 5 parts by mass or less.

A hydrophobic polymer dispersant may be used in combination with a surfactant in order to further improve dispersion stability at the time of polymerization. The hydrophobic polymeric dispersant is preferably selected to be dissolved or dispersed in the petroleum hydrocarbon dispersion medium to be used. For example, the hydrophobic polymeric dispersant may have a viscosity average molecular weight of 20,000 or less, preferably 10,000 or less, more preferably 5,000 or less . Specific examples thereof include maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, maleic anhydride-modified ethylene-propylene copolymer, maleic anhydride-ethylene copolymer, maleic anhydride-propylene copolymer, maleic anhydride- Polypropylene, ethylene-propylene copolymer, oxidized polyethylene, oxidized polypropylene, oxidized ethylene-propylene copolymer, ethylene-acrylic acid copolymer, ethylcellulose, maleic anhydride polybutadiene, maleic anhydride EPDM Ethylene / propylene / diene terpolymer) and the like.

Of these, maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, maleic anhydride-modified ethylene-propylene copolymer, maleic anhydride-ethylene copolymer, maleic anhydride-propylene copolymer, maleic anhydride- At least one member selected from the group consisting of polyethylene, polypropylene, ethylene / propylene copolymer, oxidized polyethylene, oxidized polypropylene and oxidized ethylene / propylene copolymer is preferable.

The addition amount of the hydrophobic polymeric dispersant is preferably 0 to 5 parts by mass, more preferably 0.01 to 3 parts by mass, and even more preferably 0.05 to 2 parts by mass, per 100 parts by mass of the aqueous ethylenically unsaturated monomer aqueous solution. The addition amount of the hydrophobic polymeric dispersant is 5 parts by mass or less, which is economically advantageous.

When the water-soluble ethylenically unsaturated monomer aqueous solution is added to a petroleum hydrocarbon dispersion medium charged in advance in the polymerization reactor and dispersed by a stirring part, stirring conditions by the stirring part are different depending on the desired dispersion liquid diameter, You can not decide. The diameter of the dispersed droplet can be controlled depending on the type of agitating blades of the agitating part, the blade diameter, the number of rotations, and the like. Examples of the stirring blades include propeller blades, paddle blades, anchor blades, turbine blades, Pawlinder blades, ribbon blades, full-width blades (manufactured by Shinko Pantech Co., Ltd.), Max blend blades (manufactured by Sumitomo Jukikagyo Kogyo Co., Ltd.) ), Super Mix (manufactured by Satake Kagaku Kagaku Kogyo K.K.), and the like can be used.

In the polymerization reactor, the water-soluble ethylenically unsaturated monomer aqueous solution added to the petroleum hydrocarbon dispersion medium at a predetermined addition rate is sufficiently stirred and dispersed in the petroleum hydrocarbon dispersion medium in the presence of the surfactant to stabilize the droplet. Then, the inside of the polymerization reactor is thoroughly purged with nitrogen, and if necessary, reversed-phase suspension polymerization is carried out with a water-soluble radical polymerization initiator in the presence of an internal crosslinking agent to obtain a suspension of the water-containing gel crosslinked polymer.

Examples of the water-soluble radical polymerization initiator used in the present embodiment include persulfates such as potassium persulfate, ammonium persulfate and sodium persulfate; Peroxides such as hydrogen peroxide; Azo compounds such as 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis [N- (2-carboxyethyl) -2-methylpropiononediamine] Azo compounds such as 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) -propionamide] and the like .

Of these, potassium persulfate, ammonium persulfate, sodium persulfate, and 2,2'-azobis (2-amidinopropane) dihydrochloride are preferable from the viewpoint of easy availability and easy handling.

The water-soluble radical polymerization initiator may be used as a redox polymerization initiator in combination with a reducing agent such as a sulfite or an ascorbic acid.

The amount of the water-soluble radical polymerization initiator to be used is usually 0.01 to 1 part by mass per 100 parts by mass of the water-soluble ethylenic unsaturated monomer. By lowering the polymerization rate to 0.01 part by mass or more, it is possible to inhibit the polymerization reaction from occurring at a low rate and by suppressing the occurrence of the rapid polymerization reaction by 1 part by mass or less.

The timing of adding the water-soluble radical polymerization initiator is not particularly limited, but it is preferable to add the water-soluble ethylenically unsaturated monomer aqueous solution in advance.

As the internal crosslinking agent to be used, for example, (poly) ethylene glycol ("(poly)" means a case with and without a prefix of "poly". Polyunsaturated polyesters having two or more vinyl groups obtained by reacting polyols and unsaturated acids such as acrylic acid and methacrylic acid, polyunsaturated polyesters such as N, N &lt; RTI ID = 0.0 &gt; (Poly) ethylene glycol diglycidyl ether, (poly) ethylene glycol triglycidyl ether, (poly) glycerin diglycidyl ether, (poly) glycerin triglycidyl Polyglycidyl compounds containing two or more glycidyl groups such as diallyl ether, (poly) propylene glycol polyglycidyl ether, and (poly) glycerol polyglycidyl ether. These may be used alone or in combination of two or more.

The addition amount of the internal crosslinking agent is preferably 0 to 3 parts by mass, more preferably 0 to 1 part by mass, and even more preferably 0.001 to 0.1 part by mass, per 100 parts by mass of the water-soluble ethylenic unsaturated monomer. When the addition amount is 3 parts by mass or less, excessive crosslinking is suppressed and the absorption performance is prevented from being too low. It is preferable to add the internal crosslinking agent to the water-soluble ethylenically unsaturated monomer aqueous solution in advance.

The reaction temperature in the reversed-phase suspension polymerization in the polymerization reactor varies depending on the kind and amount of the polymerization initiator to be used, and therefore can not be determined uniformly, but is preferably 30 to 100 占 폚, more preferably 40 to 90 占 폚. The reaction temperature can be suppressed from being lowered by 30 DEG C or more and the reaction temperature can be controlled to 100 DEG C or less to suppress the rapid polymerization reaction.

The polymerization reaction liquid (the suspension of the water-containing gel-like crosslinked polymer) containing the water-containing gel-state crosslinked polymer thus obtained is subjected to the first-stage polymerization and then the polymerization is repeated by adding an aqueous solution of the water- Polymerization "may be performed. Particularly, in use for sanitary materials, it is preferable to carry out two-stage polymerization in view of the size of the obtained water absorbent resin particles and the production efficiency.

The size of the particles obtained by polymerization of the water-soluble ethylenically unsaturated monomer in the first step is preferably 20 to 200 占 퐉, more preferably 30 to 150 占 퐉, in terms of the median particle size from the viewpoint of obtaining a suitable agglomerated particle diameter in the multistage polymerization, More preferably 40 to 100 mu m. Further, the median particle diameter of the first-stage polymerized particles can be measured by dehydrating and drying after completion of the first-stage polymerization.

In the case of performing the two-step polymerization, the particles obtained in the first-stage polymerization are agglomerated in accordance with the method described later to obtain an absorbent resin having a relatively large average particle diameter suitable for use in sanitary materials.

At this time, it is necessary to lower the action of the surfactant so that the water-soluble ethylenic unsaturated monomer aqueous solution used for the second stage polymerization does not form independent droplets. For example, the coagulated particles can be obtained by adding a water-soluble ethylenically unsaturated monomer aqueous solution of the second polymerization at a temperature at which cooling is performed after the completion of the first-stage polymerization and at least a part of the surfactant is precipitated.

In addition, the method is not limited to the above-mentioned method insofar as the method of obtaining the aggregated particles by adding the water-soluble ethylenically unsaturated monomer aqueous solution of the second polymerization.

In addition, the residual amount of the petroleum hydrocarbon dispersion medium in the water absorbent resin can be further reduced by adding the water-soluble ethylenically unsaturated monomer aqueous solution of the second stage polymerization after the surfactant is reduced in surfactant activity as described above.

As the water-soluble ethylenic unsaturated monomer in the second polymerization, the same ones as those exemplified as the water-soluble ethylenic unsaturated monomer in the first polymerization may be used, but the type of monomer, neutralization degree, neutralized salt and aqueous monomer solution concentration Of the water-soluble ethylenic unsaturated monomer.

The polymerization initiator to be added to the water-soluble ethylenically unsaturated monomer aqueous solution of the second polymerization may also be selected from those exemplified as the water-soluble ethylenic unsaturated monomer of the first polymerization.

If necessary, an internal cross-linking agent, a chain transfer agent and the like may be added to the water-soluble ethylenic unsaturated monomer aqueous solution of the second-stage polymerization. The water-soluble ethylenic unsaturated monomer may be selected from those exemplified as the water-soluble ethylenic unsaturated monomer in the first step polymerization.

The amount of the water-soluble ethylenic unsaturated monomer to be polymerized in the second step with respect to 100 parts by mass of the water-soluble ethylenic unsaturated monomer in the first polymerization is preferably from 50 to 300 parts by mass, more preferably from 100 to 200 parts by mass, from the viewpoint of obtaining suitable aggregated particles And most preferably 120 to 160 parts by mass.

Stirring by the stirring part in the reversed-phase suspension polymerization in the second step may be performed by uniformly mixing the whole. The agglomerated particle diameter can be changed according to the precipitation state of the surfactant or the amount of the water-soluble ethylenically unsaturated monomer of the second stage polymerization to the water-soluble ethylenically unsaturated monomer of the first stage polymerization. The aggregated particle diameter of the water absorbent resin suitable for sanitary material use is preferably 200 to 600 占 퐉, more preferably 250 to 500 占 퐉, and most preferably 300 to 450 占 퐉.

The reaction temperature in the second-stage reversed-phase suspension polymerization also varies depending on the kind and amount of the polymerization initiator, so that it can not be determined uniformly, but is preferably 30 to 100 占 폚, more preferably 40 to 90 占 폚. In the case of carrying out the multistage polymerization in two or more stages, the subsequent second stage polymerization can be carried out by reading and changing the third and fourth stages.

<Concentration Process>

The concentration step (s12) is a step of distilling off the liquid component from the polymerization reaction solution obtained by the polymerization step (s11) and concentrating the polymerization reaction solution.

The distillation treatment of the liquid component from the polymerization reaction liquid in the concentration step (s12) may be performed under atmospheric pressure or under reduced pressure, or may be carried out under a stream of air such as nitrogen in order to increase the efficiency of distillation removal of the liquid component.

When the distillation removal treatment of the liquid component from the polymerization reaction liquid is carried out under atmospheric pressure, the set temperature at the time of concentration is preferably 70 to 250 ° C, more preferably 80 to 180 ° C, further preferably 80 to 140 ° C, &Lt; / RTI &gt; to &lt; RTI ID = When the distillation removal treatment of the liquid component from the polymerization reaction liquid is carried out under reduced pressure, the set temperature at the time of concentration is preferably 60 to 100 占 폚, more preferably 70 to 90 占 폚.

&Lt; Surface cross-linking step &

In the surface cross-linking step (s13), a surface cross-linking agent containing two or more functional groups having reactivity with the functional group derived from the water-soluble ethylenic unsaturated monomer is added during the distillation removal treatment of the liquid component from the polymerization reaction liquid, Thereby increasing the density. The crosslinking density of the surface layer of the water absorbent resin particles is increased by the addition of a surface cross-linking agent after the polymerization, and the performance such as absorbency under pressure, absorption rate, gel strength and the like can be enhanced, thereby giving suitable performance for sanitary material applications.

The surface crosslinking agent used in the crosslinking reaction is not particularly limited as long as it can react with the functional group derived from the water-soluble ethylenic unsaturated monomer used for polymerization.

Examples of the surface cross-linking agent to be used include polyols such as ethylene glycol, propylene glycol, 1,4-butanediol, trimethylol propane, glycerin, polyoxyethylene glycol, polyoxypropylene glycol and polyglycerin; (Poly) ethylene glycol diglycidyl ether, (poly) ethylene glycol triglycidyl ether, (poly) glycerin diglycidyl ether, (poly) glycerin triglycidyl ether, (poly) propylene glycol polyglycidyl ether , Polyglycidyl compounds such as (poly) glycerol polyglycidyl ether; Epichlorohydrin, epichlorohydrin, epichlorohydrin, epichlorohydrin, epichlorohydrin, epichlorohydrin, epichlorohydrin, epichlorohydrin, epichlorohydrin, epichlorohydrin, epichlorohydrin, A compound having two or more reactive functional groups such as an isocyanate compound such as 2,4-tolylene diisocyanate and hexamethylene isocyanate; Ethyl-3-oxetane methanol, 3-methyl-3-oxetane methanol, 3-methyl- Oxetane compounds such as 3-butyl-3-oxetane ethanol, oxazoline compounds such as 1,2-ethylene bis oxazoline, and carbonate compounds such as ethylene carbonate. These may be used alone or in combination of two or more.

(Poly) ethylene glycol diglycidyl ether, (poly) ethylene glycol triglycidyl ether, (poly) glycerin diglycidyl ether, (poly) glycerin triglycidyl ether, (poly) ethylene glycol diglycidyl ether, ) Polyglycidyl compounds such as propylene glycol polyglycidyl ether and (poly) glycerol polyglycidyl ether are preferable.

The addition amount of the surface cross-linking agent is preferably 0.01 to 5 parts by mass, and more preferably 0.02 to 3 parts by mass based on 100 parts by mass of the total amount of the water-soluble ethylenically unsaturated monomers provided for polymerization. The addition amount of the crosslinking agent after the addition of the crosslinking agent is not less than 0.01 part by mass, it is possible to enhance the performance of the water absorbent resin under pressure, such as absorption capacity, absorption rate, gel strength and the like, and 5 parts by mass or less.

The surface cross-linking agent may be added as the surface cross-linking agent or as an aqueous solution, but may be added as a solution using a hydrophilic organic solvent as a solvent. Examples of the hydrophilic organic solvent include lower alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol and propylene glycol, ketones such as acetone and methyl ethyl ketone, diethyl ether, dioxane, Amides such as N, N-dimethylformamide, and sulfoxides such as dimethylsulfoxide, and the like. These hydrophilic organic solvents may be used alone or in combination of two or more.

The surface cross-linking agent may be added at any time after the polymerization is completed, and is not particularly limited. The surface cross-linking reaction is preferably carried out in the presence of water in the range of 1 to 200 parts by mass based on 100 parts by mass of the water absorbent resin during the distillation removal treatment of the liquid component from the polymerization reaction liquid, and the presence of water in the range of 5 to 100 parts by mass More preferably 10 to 50 parts by mass of water, and still more preferably 10 to 50 parts by mass of water. By adjusting the water content at the time of addition of the surface cross-linking agent as described above, the surface cross-linking of the surface layer of the water absorbent resin can be performed more suitably, and excellent absorption performance can be exhibited.

The temperature in the surface cross-linking reaction is preferably 50 to 250 占 폚, more preferably 60 to 180 占 폚, still more preferably 60 to 140 占 폚, and most preferably 70 to 120 占 폚.

As described above, the polymer obtained through the polymerization step (s11), the condensation step (s12) and the surface cross-linking step (s13) is usually a water-containing gel-like cross-linked polymer and is subjected to a drying treatment, a pulverizing treatment and a classification treatment, if necessary.

<Drying step>

The drying step (s14) is a step of drying the water-containing gel-like crosslinked polymer obtained in the surface cross-linking step (s13).

Examples of the drying treatment method in the drying step (s14) include heat drying, hot air drying, vacuum drying, infrared drying, microwave drying, dehydration by azeotropic distillation with a hydrophobic organic solvent, high-humidity drying using high temperature steam, But various methods can be adopted so as not to be particularly limited. When the drying treatment is carried out by hot air drying, the drying is generally carried out at a temperature of 60 to 250 ° C, preferably 100 to 220 ° C, more preferably 120 to 200 ° C (hot air temperature). The drying time is selected so as to be a desired water content depending on the surface area of the polymer, the water content, and the type of the dryer. For example, the drying time may be appropriately selected within a range of 1 minute to 5 hours.

The water content of the water absorbent resin particles that can be used in the present invention is preferably 20 mass% or less, and more preferably 10 mass% or less. By setting the moisture content of the water absorbent resin particles to 20 mass% or less, good fluidity of the water absorbent resin particles can be maintained.

&Lt; Crushing process >

The pulverizing step (s15) is a step of pulverizing the granular or dry particulate dry aggregate obtained in the drying step (s14) using a pulverizer. The pulverizer used in the pulverizing process (s15) is not particularly limited, and examples thereof include roll mills such as roll mills, hammer mills such as hammer mills, impact mills, cutter mills, turbo grinders, ball mills, do. Among them, a roll mill is preferable for controlling the particle diameter distribution. In order to control the particle diameter distribution, it may be pulverized two or more times in succession, or may be pulverized three or more times. In the case of grinding more than twice, each grinder may be the same or different. Further, other types of pulverizers may be used in combination.

<Classification Process>

The classification step (s16) is a step of classifying the pulverized product obtained in the pulverization step (s15). In the classification step (s16), the crushed material is sieved. In this classification step (s16), particles having a desired particle diameter (preferably a weight average particle diameter of 200 to 800 mu m) are selected to obtain the desired water absorbent resin particles. The classification method is not particularly limited, and conventionally known methods can be employed. Although it is not particularly limited, it is preferable to use a body classification (metal body, made of stainless steel). Further, in order to achieve desired physical properties and particle size, it is preferable to use a plurality of sieves simultaneously in the classification step (s16).

In the resin particle preparation step (s1) having the polymerization step (s11), the concentration step (s12), the surface cross-linking step (s13), the drying step (s14), the pulverization step (s15) and the classification step (s16) And the prepared water absorbent resin particles are provided in the mixing step (s2).

[Mixing Process]

3 is a process diagram showing an example of details of the mixing process (s2). 4 is a diagram showing an example of the configuration of the mixing equipment 1 for carrying out the mixing step s2. In the mixing step (s2), the water absorbent resin particles and the additive particles prepared in the resin particle preparing step (s1) are mixed in multiple stages using a plurality of mixing devices to obtain the water absorbent resin composition. For example, (S21), a first transport mixing process (s22), a second mixing process (s23), and a second transport mixing process (s24). Each step in the mixing step s2 is carried out, for example, by the mixing equipment 1 shown in Fig.

The mixing apparatus 1 includes an additive particle hopper 11, an absorbent resin particle hopper 12, a first mixing device 13, a first compressor 14, a second mixing device 15 and a second compressor 16, And a water absorbent resin composition hopper 17.

The additive particle hopper 11 receives additive particles. The additive particle contained in the additive particle hopper 11 is not particularly limited as long as it is a powder capable of imparting an additional function such as moisture absorption and blocking property to the water absorbent resin composition to be produced, and conventionally known knowledge can be appropriately referred to. Examples of the additive particles include powders (organic powders) composed of organic materials such as pulp powders, cellulose derivatives and natural polysaccharides, powders (inorganic powders) composed of inorganic materials, antioxidants, preservatives, bactericides, surfactants, , Deodorant and the like are exemplified.

Among these additive particles, for example, when imparting moisture absorption and blocking resistance, inorganic powder is preferable, and water-insoluble inorganic powder is particularly preferable. Examples of the inorganic powder include ceramic powders such as calcium carbonate, kaolin, talc, mica, bentonite, clay, sericite, asbestos, glass fiber, carbon fiber, glass powder, glass balloon, shirasu balloon, coal powder, metal powder, alumina, , Zeolite, activated carbon and slate powder.

The water absorbent resin particle hopper 12 accommodates the water absorbent resin particles obtained by the resin particle preparing step (s1).

The additive particle hopper 11 is connected to the first mixing device 13 through the additive particle supply pipe 21. [ The water absorbent resin particle hopper 12 is connected to the first mixing device 13 through the water absorbent resin particle feed pipe 22. The additive particles contained in the additive particle hopper 11 are supplied to the first mixing device 13 through the additive particle feed pipe 21 and the water absorbent resin particles contained in the water absorbent resin particle hopper 12 are absorbed And is supplied to the first mixing device 13 through the resin particle feed pipe 22.

&Lt; Primary mixing step &

The primary mixing step (s21) is a primary mixing step in the mixing step (s2) in which the water absorbent resin particles and the additive particles are primarily mixed using the first mixing device (13).

As the first mixing device 13 used in the primary mixing process (s21), an air-flow type mixer or a rotary mixing type mixer can be exemplified as a continuous or batch type mixer, and a rotary mixing type mixer is preferably used . The first mixing device 13 may be a continuous mixer such as a conical blender, a nauta mixer, a kneader, a V-type mixer, a flow mixer, a turbulizer, a Lodige mixer, a screw mixer, a ribbon blender, a silo blender, Or batch mechanical mixers are exemplified. In such a rotary stirring type mixer, the stirring blade is usually rotated at 10 to 10,000 rpm and further at 100 to 5,000 rpm.

In the primary mixing step (s21) carried out by the first mixing device 13, the treatment temperature of the primary mixing treatment is set to, for example, 10 to 100 占 폚. The treatment time of the primary mixing treatment in the primary mixing step (s21) is appropriately set according to the throughput, but is set to, for example, 1 to 10 minutes / t (ton).

In addition, the mixing ratio of the water absorbent resin particles and the additive particles mixed in the primary mixing step (s21) is not particularly limited, and the desired absorption characteristics and other characteristics of the water absorbent resin composition to be produced, . For example, the mixing ratio (mass ratio) of the water absorbent resin particles to the additive particles is preferably 100: 0.01 to 100: 1 (water absorbent resin particles: additive particles), more preferably 100: 0.1 to 100: 0.7 Resin particles: additive particles), and more preferably 100: 0.2 to 100: 0.5 (absorbent resin particles: additive particles). When the mixing ratio of the additive particles is 0.01 or more, the water absorption blocking ratio of the water absorbent resin composition to be obtained is maintained at a low value and the water absorption and flow property is excellent. On the other hand, when the mixing ratio of the additive particles is 1 or less, the water absorbent resin composition to be obtained is preferable because it has excellent absorption capacity under pressure (absorption under pressure). However, it goes without saying that a form deviating from these ranges may be employed.

The primary mixing step (s21) preferably further comprises a plurality of mixing steps. (S21) in which the water absorbent resin particles and the additive particles are first mixed is further subjected to a plurality of mixing steps so that the total amount of the water absorbent resin particles and the additive particles, which are the raw materials necessary for producing the water absorbent resin composition, In the mixing step (s21), the primary mixture can be obtained by dividing into a plurality of portions in each mixing step.

Further, in the primary mixing step (s21) having a plurality of mixing steps, the throughput of the primary mixing treatment in each mixing step is preferably such that the throughput of the water absorbent resin particles is more than 0 (zero) and not more than 40,000 kg, More preferably greater than 0 and less than 20,000 kg, more preferably greater than 0 and less than 10,000 kg. This makes it possible to improve the dispersibility of the additive particles in the primary mixture obtained by the primary mixing step (s21).

The primary mixture obtained by the first mixing device 13 is supplied to the first transport pipe 24 through the primary mixture deriving pipe 23 by opening the first opening / closing valve 23a. The first transport pipe 24 is disposed between the first mixing device 13 and the second mixing device 15.

<First Transportation Mixing Step>

The first transport mixing process (s22) is a process in which the primary mixture obtained in the primary mixing process (s21) is vapor-phase transported through the first transport pipe (24) to mix the primary mixture in the first transport pipe And the first transporting and mixing step in the mixing step s2.

Compressed air generated by the first compressor 14, which is connected to one end of the first transport pipe 24, flows through the first transport pipe 24 and flows through the first mixture pipe 23, The primary mixture supplied to the transport pipe 24 is transported toward the second mixing device 15 by the flow of the compressed air by the first compressor 14, and is mixed at the time of transportation. The first compressor (14) and the first transportation piping (24) constitute a vapor phase transportation device.

The gas phase transportation device constituted by the first compressor 14 and the first transportation pipeline 24 is not particularly limited and may be, for example, a plug-type air transportation system, a secondary oil pipe storage air transportation system, a sliding fluidized- , Suspended dispersion type air transportation system, and the like.

In the meteorological transport apparatus, the plug-type air transportation system is one of the transportation modes in which the powder (primary mixture) is moved (transported) while forming a group of plugs without floating. Such a gas-phase transport apparatus of the plug-type air-transport system has a small air consumption and is excellent in transport efficiency and has a very small amount of crushing of the transported product (primary mixture) and wear of the first transport pipe 24. Further, the gaseous transport device of the plug-type air transportation system also has a feature that almost no streamer is generated when the resin pellets are transported.

In the meteorological transporter, the brine storage air transportation mode is a mode of transportation in which the air velocity is comparatively slow and the powder (primary mixture) is concentrated on the bottom of the first transport pipe 24 among the classifications classified by the counter oil. This gas-phase transport system of the retained-pipe-type air-transportation system has a higher mixing ratio than that of the system using the dispersed-flow system, and thus has excellent transport efficiency, and is less susceptible to crushing of the transported product (primary mixture) and wear of the first transport pipe 24 will be.

In the meteorological transport apparatus, the sliding fluidized-bed air transportation system is a system in which the powder (primary mixture) is transported (transported) in the form of a mass flow like sand dune at the site of the first transport pipe 24 Transportation mode. Although the gas phase transport apparatus of the sliding fluidized-bed air transportation system is almost the same as the formation of the plug-like air transportation system in the case of coarse powder, There is a characteristic that there is no, or very little, blocking portion.

In weather-based transportation equipment, the suspended dispersion type air transportation system is a transportation type in which the powder (primary mixture) is moved while it is flying. The air-phase transport apparatus of the floating dispersion type air transportation system belongs to a so-called low-concentration transportation in which the wind velocity in the first transportation pipeline 24 is high.

The processing conditions of the transport mixing process in the first transport mixing process (s22) carried out by the gas phase transport apparatus constituted by the first compressor 14 and the first transport pipeline 24 are the same as those of the first mixture It is suitably set in accordance with the throughput and the transportation distance. Specifically, the air pressure at the time of vapor-phase transportation (the pressure of the compressed air generated by the first compressor 14) is preferably set at 0.01 to 10 MPa, and more preferably at 0.01 to 1 MPa.

The total length of the first transport pipeline 24 is preferably set to 1 to 2,000 m, more preferably to 10 to 300 m. The inner diameter of the first transport pipe 24 is preferably set to 10 to 400 mm, and more preferably to 30 to 300 mm.

The throughput of the transport mixing process in the first transport mixing process (s22) is preferably set at 1,000 to 30,000 kg / hour, more preferably 1,000 to 20,000 kg / hour. The treatment time of the transporting and mixing treatment in the first transporting and mixing step (s22) is preferably set to 0.01 to 30 minutes, and more preferably 0.1 to 10 minutes. In addition, the treatment temperature of the transporting and mixing treatment in the first transporting and mixing step (s22) is preferably set at 10 to 100 占 폚, and more preferably at 20 to 90 占 폚.

The transport wind speed (end transport wind speed) at the end of the first transport pipeline 24 on the outlet side (the second mixing apparatus 15 side) is preferably set to 0.1 to 30 m / sec, 15 m / sec. The solid / gas ratio (terminal solid / gas ratio) at the outlet side (on the side of the second mixing device 15) of the first transport pipeline 24 is preferably 1 to 200 kg-Solid / kg-Air And more preferably 5 to 100 kg-Solid / kg-Air.

In the above description, the primary mixture obtained by the first mixing device 13 is vapor-phase-transported to the second mixing device 15 by the vapor phase transport device constituted by the first compressor 14 and the first transport pipe 24 However, the method of transporting the primary mixture to the second mixing device 15 is not limited to this vapor-phase transporting method. Examples of a device for realizing another method of transporting the primary mixture to the second mixing device 15 include a conveying device such as a screw conveyor, a spring conveyor, a belt conveyor, a bucket conveyor, and a vibration feeder, Apparatus is preferred. More preferably, the conveying device is a non-open type conveying device in which a portion for accommodating a gaseous phase portion in the conveyor, that is, a primary mixture or the like, is partitioned by, for example, a partition plate or a screw.

All of the vapor phase transport apparatus constituted by the first compressor 14 and the first transport pipeline 24 and the above transport apparatus can be easily transported without deteriorating the continuous transportability by mounting a discharge port and a rotary valve, etc., Thereby realizing non-open circuit. It is a weather conveyance device or a screw conveyor, particularly a weather conveyance device, which can be easily realized without releasing. Further, the vapor phase transport apparatus is particularly excellent also in the effect of promoting the mixing of the primary mixture.

The primary mixture obtained by the first mixing device 13 is supplied to the second mixing device 15 while being vapor-phase transported through the first transport pipe 24 and mixed in the first transport pipe 24.

&Lt; Secondary mixing step &

In the secondary mixing step s23, the primary mixture mixed in the first transportation pipe 24 is introduced into the primary mixture through the second mixing device 15 until the additive particles are uniformly dispersed, And the second mixing step in the mixing step (s2) for mixing.

As the second mixing device 15 used in the secondary mixing step s23, as in the first mixing device 13 described above, an airflow type mixer or a rotation stir mixer can be exemplified as a continuous or batch type mixer , Particularly a rotary stirring type mixer is preferably used. Examples of the second mixing device 15 include a continuous mixer such as a conical blender, a Nauta mixer, a kneader, a V-type mixer, a flow mixer, a turbulizer, a Lodige mixer, a screw mixer, a ribbon blender, a silo blender, Or batch mechanical mixers are exemplified. In such a rotary stirring type mixer, the stirring blade is usually rotated at 10 to 10,000 rpm and further at 100 to 5,000 rpm.

It is preferable that the second mixing device 15 used in the secondary mixing process s23 is a mixing device different from the first mixing device 13 described above. Thus, the first mixing device 13 used in the primary mixing step (s21) for primary mixing the water absorbent resin particles and the additive particles to obtain a primary mixture, and the first mixing device 13 for secondary mixing the primary mixture, The second mixing apparatus 15 used in the second mixing step s23 to obtain the water absorbent resin composition of the present invention has a different mixing system, so that the water absorbent resin composition in which the additive particles are more uniformly dispersed can be obtained in a short time.

In the secondary mixing step (s23) performed by the second mixing device 15, the treatment temperature of the secondary mixing treatment is set to, for example, 10 to 100 占 폚. The processing time of the secondary mixing treatment in the secondary mixing step s23 is appropriately set according to the throughput, but is set to, for example, 1 to 10 minutes / t (ton).

The secondary mixture obtained by the second mixing device 15 is supplied to the second transportation pipe 26 through the secondary mixture deriving pipe 25 by opening the second opening / closing valve 25a. The second transport pipe 26 is disposed between the second mixing device 15 and the water absorbent resin composition hopper 17. A switching valve 26a is provided in the second transportation pipe 26 and a circulation pipe 27 is provided so as to branch off from the position where the switching valve 26a of the second transportation pipe 26 is disposed have. This circulation pipe 27 is disposed between the switching valve 26a and the second mixing device 15. [ The secondary mixture supplied from the second mixing device 15 to the second transporting pipe 26 is returned to the second mixing device 15 when the switching valve 26a is switched to the second mixing device 15 side , And when the switching valve 26a is switched to the water absorbent resin composition hopper 17 side, it is vapor-phase transported toward the water absorbent resin composition hopper 17. [

&Lt; Second Transport Mixing Process >

The second transport mixing process (s24) is a process of mixing the secondary mixture in the second transport pipe 26 by vapor-phase transporting the secondary mixture obtained in the secondary mixing process (s23) through the second transport pipe 26 Is the second transport mixing step in the process (s2).

Compressed air generated by the second compressor 16, which is connected to one end of the second transfer piping 26, flows through the second transfer piping 26 and flows through the second mixture piping 25 to the second The secondary mixture supplied to the transport piping 26 is discharged toward the water absorbent resin composition hopper 17 by the flow of the compressed air by the second compressor 16 and is transported and mixed at the time of transportation. The second compressor (16) and the second transport pipe (26) constitute a vapor transport device.

The vapor phase transport apparatus constituted by the second compressor 16 and the second transport pipeline 26 is constructed in the same manner as the gas phase transport apparatus constituted by the first compressor 14 and the first transport pipeline 24 described above, The secondary mixture supplied to the second transport pipe 26 is transported while blocking the second transport pipe 26 in the form of a plug.

The processing conditions of the transport mixing process in the second transport mixing process (s24) carried out by the gas phase transport device constituted by the second compressor (16) and the second transport pipe (26) It is suitably set in accordance with the throughput and the transportation distance. Specifically, the air pressure at the time of vapor-phase transportation (the pressure of the compressed air generated by the second compressor 16) is preferably set at 0.01 to 10 MPa, and more preferably at 0.01 to 1 MPa.

The total length of the second transport pipe 26 is preferably set to 1 to 2,000 m, more preferably to 10 to 300 m. The inner diameter of the second transport pipe 26 is preferably set to 10 to 400 mm, and more preferably to 30 to 300 mm.

The throughput of the transporting mixing process in the second transport mixing process (s24) is preferably set at 1,000 to 30,000 kg / hour, more preferably 1,000 to 20,000 kg / hour. The treatment time of the transporting and mixing treatment in the second transporting and mixing step (s24) is preferably set to 0.01 to 30 minutes, more preferably 0.1 to 10 minutes. In addition, the treatment temperature of the transporting and mixing treatment in the second transporting and mixing step (s24) is preferably set to 10 to 100 占 폚, and more preferably to 20 to 90 占 폚.

The transport wind speed (end transport wind speed) at the end of the second transport pipeline 26 (on the side of the water absorbent resin composition hopper 17) is preferably set to 0.1 to 30 m / sec, 15 m / sec. The solid / gas ratio (terminal solid / gas ratio) at the outlet side (on the side of the water absorbent resin composition hopper 17) of the second transportation pipeline 26 is preferably 1 to 200 kg-Solid / kg-Air And more preferably 5 to 100 kg-Solid / kg-Air.

The secondary mixture obtained by the second mixing device 15 is supplied to the water absorbent resin composition hopper 17 while being vapor-phase transported through the second transport pipe 26 and mixed in the second transport pipe 26.

The water absorbent resin composition obtained in the mixing step (s2) having the primary mixing step (s21), the first transportation mixing step (s22), the secondary mixing step (s23) and the second transportation mixing step (s24) Is provided to the recovery process (s3).

[Recovery process]

The recovery step s3 is a step of recovering the water absorbent resin composition obtained in the mixing step s2 to the water absorbent resin composition hopper 17 functioning as a recovery tank.

In the second transportation and mixing step (s24) described above, the water absorbent resin composition gas-phase-transported in the second transport pipe 26 flows into the water absorbent resin composition hopper 17. [ As described above, the water absorbent resin composition introduced into the water absorbent resin composition hopper 17 is contained in the water absorbent resin composition hopper 17.

In the method for producing the water absorbent resin composition of the present embodiment, the mixing procedure for obtaining the water absorbent resin composition in which the additive particles of the predetermined concentration are mixed with the water absorbent resin particles includes the following four steps (a) to (d) Mixing order may be any.

(a) The total amount of the water absorbent resin particles and additive particles serving as raw materials corresponding to the target production amount of the water absorbent resin composition is primarily mixed in the primary mixing step (s21). Then, the total amount of the primary mixture obtained in the primary mixing step (s21) (the total amount of the primary mixture obtained in each of the mixing steps when the primary mixing step (s21) has a plurality of mixing steps) And the second mixture is carried out in the step (s23).

(b) the smaller amount of the water absorbent resin particles and the additive particles are primarily mixed in the primary mixing step (s21) with respect to the target production amount of the water absorbent resin composition. Then, the remainder of the water-absorbent resin particles is added to the total amount of the primary mixture obtained in the primary mixing step (s21), and the water-absorbent resin particles are secondarily mixed in the secondary mixing step (s23).

(c) The smaller amount of the additive particles and the water absorbent resin particles are primarily mixed in the primary mixing step (s21) with respect to the target production amount of the water absorbent resin composition. Then, the residue of the additive particles is added to the total amount of the primary mixture obtained in the primary mixing step (s21), followed by secondary mixing in the secondary mixing step (s23).

(d) The smaller amount of the water absorbent resin particles and the additive particles are primarily mixed in the primary mixing step (s21) with respect to the target production amount of the water absorbent resin composition. Then, the water absorbent resin particles and the remnants of the additive particles are added to the total amount of the primary mixture obtained in the primary mixing step (s21), and the water-absorbent resin particles and secondary particles are mixed in the secondary mixing step (s23).

In the method of producing the water absorbent resin composition of the present embodiment, the water absorbent resin particles and the additive particles are mixed in multiple stages using a plurality of mixing devices (the first mixing device 13 and the second mixing device 15) It is possible to obtain the water absorbent resin composition in which the additive particles are uniformly dispersed in a short time without damaging the surface of the water absorbent resin composition. Accordingly, it is possible to obtain a water absorbent resin composition in which the additive particles such as moisture absorption blocking resistance and the like exhibit sufficient additional functions while maintaining excellent absorption properties.

Further, when the water absorbent resin particles and the additive particles are mixed with each other in a production facility having a large production amount of the water absorbent resin composition, it becomes difficult to obtain the water absorbent resin composition in which the additive particles are uniformly dispersed. In the method of producing the water absorbent resin composition of the present embodiment, since the water absorbent resin particles and the additive particles are mixed in multiple stages using a plurality of mixing devices, even when the water absorbent resin particles and the additive particles are mixed in a large- The water-absorbent resin composition can be obtained in a short period of time.

Example

Hereinafter, the present invention will be described in detail with reference to Examples of the present invention, but the present invention is not limited to the following Examples.

[Preparation of water absorbent resin particles]

First, the water-soluble ethylenically unsaturated monomer was subjected to two-step polymerization reaction in the presence of a dispersion stabilizer in a petroleum hydrocarbon dispersion medium by a reversed-phase suspension polymerization method using a radical polymerization initiator to produce an absorbent resin.

Concretely, n-heptane maintained at a temperature of 25 캜 as a petroleum hydrocarbon dispersion medium in the polymerization reactor at the time of the first stage polymerization, polyglycerin fatty acid ester (trade name: SunSoft Q-185S, 10% by mass n-heptane solution (trade name, manufactured by Shikisan Co., Ltd.) was added.

Subsequently, the content in the polymerization reactor was heated to 90 deg. C while stirring in the polymerization reactor by the stirring section to dissolve the dispersion stabilizer. Then, the content in the polymerization reactor was cooled to 50 캜.

On the other hand, an aqueous solution of 80 mass% acrylic acid as a water-soluble ethylenic unsaturated monomer was added to another container and while cooling, 30 mass% sodium hydroxide aqueous solution was dropped as an alkaline neutralizing agent so that the degree of neutralization became 75 mol% of the acid value of the water-soluble ethylenic unsaturated monomer Neutralization was carried out. Subsequently, potassium persulfate as a radical polymerization initiator, N, N'-methylene bisacrylamide and N, N'-methylenebisacrylamide as a crosslinking agent and water were added and dissolved to prepare a monomer for polymerization at the first stage as an aqueous solution.

The total amount of the monomer aqueous solution for polymerization for the first stage which was maintained at a temperature of 10 캜 prepared in the other vessel as described above was added to the polymerization reactor and the content of the polymerization reactor was adjusted to 30 캜 to sufficiently replace the system with nitrogen did.

Subsequently, the content in the polymerization reactor was heated to 55 캜 while stirring in the polymerization reactor by means of a stirring section to initiate polymerization. After the initiation of the polymerization, the contents of the polymerization reactor were heated by polymerization heat, and after the content reached 80 캜, polymerization was carried out at 80 캜 for 30 minutes, and the contents of the polymerization reactor were cooled to 13 캜, Of a reaction mixture.

On the other hand, a monomer aqueous solution for polymerization for the second stage was prepared in another vessel. Specifically, 80 mass% acrylic acid aqueous solution as a water-soluble ethylenic unsaturated monomer is added to another container, and while cooling, 30 mass% sodium hydroxide aqueous solution is dropped as an alkaline neutralizing agent so that the degree of neutralization is 75 mole% of the acid group of the water-soluble ethylenic unsaturated monomer The neutralization was carried out as much as possible. Subsequently, potassium persulfate as a radical polymerization initiator, N, N'-methylenebisacrylamide and water as a crosslinking agent were added and dissolved to prepare a second monomer aqueous solution for polymerization.

The total amount of the monomer aqueous solution for polymerization in the second step, which was maintained at a temperature of 13 캜 prepared in the other vessel as described above, was charged into a polymerization reactor containing the above-mentioned reaction mixture, and the inside of the system was sufficiently substituted with nitrogen .

Subsequently, the content in the polymerization reactor was heated to 55 캜 while stirring in the polymerization reactor by means of a stirring section to initiate polymerization. After the initiation of the polymerization, the contents of the polymerization reactor were heated by the heat of polymerization and polymerization was carried out at 80 DEG C for 30 minutes from the time when the content reached 80 DEG C, to obtain the second reaction mixture.

The reaction mixture in the second stage was transferred to a concentrator, and the contents in the concentrator were heated to 90 DEG C while stirring in the concentrator by an agitator, and N-heptane and water were separated by azeotropic distillation of n-heptane and water The n-heptane was returned to the concentrator and the water was withdrawn from the system. Next, N, N'-methylenebisacrylamide was added as a crosslinking agent, and the content in the concentrator was reacted at 90 DEG C to obtain a surface cross-linked reaction mixture.

The surface cross-linked reaction mixture was transferred to a drier and heated to draw water and n-heptane out of the system, and the dried water absorbent resin was sieved with a sieve having an opening size of 850 mu m to obtain water absorbent resin particles (A1).

[Preparation of water absorbent resin composition]

(Example 1)

&Lt; Primary mixing step &

The water absorbent resin particles (A1) obtained as described above and amorphous silica (Sipernat 200, manufactured by Degussa Japan K.K., primary particle size: several nm to several tens nm) as additive particles were dispersed in a screw-type vertical rotation mixer Nauta Mixer) (Nauta Mixer NX-150, manufactured by Hosokawa Micron Corporation) to obtain a first mixture. The processing conditions of the mixing treatment in the primary mixing step using the Nauta mixer were set as follows.

Throughput: 0.5 parts by mass (50 kg) of amorphous silica was added to 100 parts by mass (10,000 kg) of the water absorbent resin particles (A1).

Processing time: 1.5 minutes / t (total 15 minutes)

· Treatment temperature: 20 ° C

<First Transportation Mixing Step>

The primary mixture thus obtained was vapor-phase transported through the first transport pipe to be mixed in the first transport pipe. The processing conditions of the transport mixing treatment in the first transport mixing step are set as follows.

· Pressure during air transportation (air pressure): 0.08MPa

Overall length and inner diameter of the first transport pipeline: total length 50 m, inner diameter 150 mm

· Throughput: 10,000 kg / hour

· Treatment time: 0.3 minutes

· Treatment temperature: 20 ° C

· Terminal velocity of the first transport pipeline: 3 m / sec

· Terminal solid / gas ratio in the first transport pipe: 60 kg-Solid / kg-Air

&Lt; Secondary mixing step &

In the first transport mixing step, the transport mixture-treated primary mixture was secondary-mixed using a recycling-type gravity silo blender (SUS silo blender, manufactured by Nippon Aluminum Co., Ltd.) to obtain a secondary mixture. Processing conditions for the mixing treatment in the secondary mixing step using the silo blender were set as follows.

Throughput: The total amount of the six primary mixtures obtained in the primary mixing process (60,000 kg)

· Processing time: 6.0 minutes / t (6 hours in total)

· Treatment temperature: 20 ° C

&Lt; Second Transport Mixing Process >

The secondary mixture thus obtained was vapor-phase transported through the second transport pipe and mixed in the second transport pipe to obtain the water absorbent resin composition of Example 1. The processing conditions of the transport mixing treatment in the second transport mixing step were set as follows.

· Pressure during air transportation (air pressure): 0.2 MPa

· Overall length and inner diameter of the second transport piping: 200 m in total length, 200 mm in inner diameter

· Throughput: 20,000 kg / hour

Processing time: 0.6 minutes

· Treatment temperature: 20 ° C

· Terminal transport wind speed of the 2nd transport pipeline: 6m / sec

· Terminal solid / gas ratio in the second transport pipe: 30 kg-Solid / kg-Air

(Example 2)

The water absorbent resin composition of Example 2 was obtained in the same manner as in Example 1 except that the secondary mixing step was performed as follows.

&Lt; Secondary mixing step &

The first mixture which has been transported and mixed in the first transport mixing process is secondarily mixed with a screw type vertical rotation type mixer (Nauta mixer) (Nauta Mixer NX-250, manufactured by Hosokawa Micron Corporation) &Lt; / RTI &gt; The processing conditions for the mixing treatment in the secondary mixing step using the Nauta mixer were set as follows.

· Throughput: The total amount of the two primary mixtures obtained in the primary mixing step (20,000 kg)

Processing time: 6.0 minutes / t (2 hours in total)

· Treatment temperature: 20 ° C

(Example 3)

Except that the addition amount of amorphous silica (Sipernat 200, manufactured by Degussa Japan K.K.) to 100 parts by weight (10,000 kg) of the water absorbent resin particles (A1) was changed from 0.5 parts by mass to 0.1 parts by mass in the primary mixing step The water absorbent resin composition of Example 3 was obtained in the same manner as in Example 1.

(Comparative Example 1)

The secondary mixing step and the second transportation mixing step were not performed. Specifically, the water absorbent resin particle (A1) and the amorphous silica (Sipernat 200, manufactured by Degussa Japan K.K.) as additive particles are mixed with a screw type vertical shaft rotary mixer (Nauta mixer) (Nauta Mixer NX-150, Hosokawa Micron Corporation Ltd.) to obtain a mixture. The processing conditions for the mixing treatment using the Nauta mixer were set as follows.

Throughput: 0.5 parts by mass (50 kg) of amorphous silica was added to 100 parts by mass (10,000 kg) of the water absorbent resin particle (A1)

Processing time: 7.5 minutes / t (75 minutes in total)

· Treatment temperature: 20 ° C

Then, the mixture thus obtained was vapor-phase transported through a transportation pipe to be mixed in the transportation pipe to obtain the water-absorbent resin composition of Comparative Example 1. [ The processing conditions of the transport mixing treatment were set as follows.

· Pressure during air transportation (air pressure): 0.08MPa

· Overall length and inner diameter of transport piping: Length 50 m, inner diameter 150 mm

· Throughput: 10,000 kg / hour

· Treatment time: 0.3 minutes

· Treatment temperature: 20 ° C

· Terminal speed of transport pipeline: 3m / sec

· Terminal solid / gas ratio in transport piping: 60kg-Solid / kg-Air

(Comparative Example 2)

(Sipernat 200, manufactured by Degussa Japan K.K.) relative to 100 parts by weight (10,000 kg) of the water absorbent resin particles (A1) was changed from 0.5 parts by mass to 0.1 parts by mass, as in Comparative Example 1 A water absorbent resin composition of Example 2 was obtained.

[Evaluation results]

The water absorbing resin compositions of Examples 1 to 3 and Comparative Examples 1 and 2 thus obtained were evaluated for the moisture absorption blocking ratio, the absorbing ability, and the absorbing ability under pressure.

<Moisture absorption blocking ratio>

10 g of the water absorbent resin composition passing through the 20-mesh sieve was uniformly placed in a cylindrical aluminum tray having a diameter of 5 cm and allowed to stand for 3 hours in a constant temperature and humidity chamber at a temperature of 40 ± 1 ° C. and a relative humidity of 80 ± 5%. After measuring the total weight a (g) of the water absorbent resin composition after being allowed to stand for 3 hours, it is filtered by tapping with a twelve mesh wire net five times and blocked by moisture absorption to measure the weight b (g) And the moisture absorption blocking ratio was determined by the following formula (1).

Moisture blocking rate (%) = (b / a) x 100 ... (One)

<Absorption Capacity>

500 g of a 0.9-mass% saline solution was added to a 500-mL beaker, 2.0 g of the water absorbent resin composition was added thereto, and the mixture was stirred for 60 minutes. The weight Wa (g) of a JIS standard having a mesh size of 75 mu m was measured in advance, and the contents of the beaker were filtered using the filter. The beaker was allowed to stand for 30 minutes while being inclined at an angle of about 30 degrees with respect to the horizontal, The water was filtered. Then, the mass Wb (g) of the body containing the absorbing gel was measured, and the absorption capacity was determined by the following equation (2).

Absorption capacity (g / g) = (Wb-Wa) /2.0 (2)

&Lt; Absorption under pressure >

The absorption capacity under pressure of the water absorbent resin composition was measured using the measuring device 3 shown schematically in Fig. 5 includes a burette section 31, a conduit 32, a measuring section 33, and a measuring section 34 provided on the measuring section 33. The measuring section 3 includes a burette section 31, The burette portion 31 is connected to the upper portion of the burette 310 with a rubber stopper and the air introduction pipe 311 and the cock 312 are connected to the lower portion of the burette 310. The air introduction pipe 311 has a coke 313 have. A conduit 32 is mounted between the burette section 31 and the measuring platform 33 and the inside diameter of the conduit 32 is 6 mm. A hole having a diameter of 2 mm is formed at the center of the measuring table 33, and a conduit 32 is connected. The measurement section 34 has a cylindrical section 340 (made of plexiglass), a nylon mesh 341 bonded to the bottom of the cylindrical section 340, and a weight 342. The inner diameter of the cylindrical portion 340 is 20 mm. The opening size of the nylon mesh 341 is 75 m (200 mesh). At the time of measurement, the water absorbent resin composition 35 was uniformly dispersed on the nylon mesh 341. The weight 342 has a diameter of 19 mm and a mass of 59.8 g. The weight 342 is placed on the water absorbent resin composition 35 so that a load of 2.07 kPa can be applied to the water absorbent resin composition 35.

Next, the measurement procedure will be described. The measurement was carried out in a room at 25 캜. First, the cock 312 and the cock 313 of the burette portion 31 were closed and 0.9 mass% saline adjusted at 25 ° C was poured from the upper portion of the burette 310. The upper portion of the burette 310 was covered with a rubber stopper The cock 312 of the hood portion 31 and the cock 313 were opened. Subsequently, the height of the measurement table 33 was adjusted so that the water surface of the 0.9 mass% saline solution discharged from the central conduit of the measurement table 33 and the upper surface of the measurement table 33 had the same height.

Separately, 0.10 g of the water absorbent resin composition 35 is uniformly dispersed on the nylon mesh 341 of the cylindrical portion 340 and the weight 342 is placed on the water absorbent resin composition 35, . Then, the center of the measuring portion 34 is aligned with the center of the measuring portion 33 at the center.

(In other words, the 0.9 mass% saline solution absorbed by the water absorbent resin composition 35) Wc (ml) is read from the time when the water absorbent resin composition 35 starts to be absorbed. The absorption capacity under pressure of the water absorbent resin composition 35 after elapse of 60 minutes from the start of absorption was determined by the following formula (3).

Absorption capacity under pressure (ml / g) = Wc / 0.10 ... (3)

The evaluation results are shown in Table 1.

As is clear from Table 1, the water absorbent resin compositions of Examples 1 to 3 obtained by secondary mixing the primary mixture obtained in the primary mixing step in the secondary mixing step had the water absorbency of Comparative Example 1 and Comparative Example 2 The moisture absorption blocking ratio is maintained at a low level while the absorption characteristics exhibited by the absorption ability and the absorption ability under pressure are maintained in a state superior to the resin composition and the moisture absorption blocking property as an additional function of the additive particles (amorphous silica) is sufficiently exhibited .

The present invention may be embodied in other various forms without departing from the spirit or essential characteristics thereof. Therefore, the above-described embodiments are merely examples in all respects, and the scope of the present invention is shown in the claims, and is not limited to the details of the specification. Modifications and variations falling within the scope of the claims are all within the scope of the present invention.

1: mixing equipment 11: additive particle hopper
12: absorbent resin particle hopper 13: first mixing device
14: first compressor 15: second mixing device
16: second compressor 17: water absorbent resin composition hopper

Claims (7)

A method for producing an water absorbent resin composition comprising water absorbent resin particles and additive particles,
A process for producing a water-absorbent resin, comprising the steps of:
And a mixing step of mixing the water absorbent resin particles prepared in the resin particle preparing step with the additive particles in multiple stages using a plurality of mixing devices to obtain an water absorbent resin composition. The method according to claim 1,
In the mixing step,
A primary mixing step of primary mixing the water absorbent resin particles and the additive particles using a first mixing device,
And a second mixing step of mixing the first mixture obtained in the first mixing step with the second mixture using the second mixing apparatus until the additive particles are uniformly dispersed. 3. The method of claim 2,
Wherein the primary mixing step further comprises a plurality of mixing steps. The method according to claim 2 or 3,
In the mixing step,
The first mixture obtained in the first mixing step is vapor-phase-transported from the first mixing device to the second mixing device through the first transfer pipe provided between the first mixing device and the second mixing device, A first transport mixing step of mixing the primary mixture in the transport piping,
The secondary mixture obtained in the secondary mixing step is discharged from the second mixing apparatus through a second transportation pipeline for discharging from the second mixing apparatus and is vapor-phase transported to mix the secondary mixture in the second transportation pipeline And a second transport mixing step of mixing the water-absorbent resin composition and the water-absorbent resin composition. 5. The method according to any one of claims 2 to 4,
Wherein the first mixing device and the second mixing device are devices of different mixing types. 6. The method according to any one of claims 1 to 5,
Wherein the additive particles are particles made of an inorganic material. 7. The method according to any one of claims 2 to 6,
Wherein in the primary mixing step, the throughput of the water absorbent resin particles in one primary mixing treatment is more than 0 and not more than 40,000 kg.

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